Techniques known in the art include obtaining, based on a received signal generated by transmitting and receiving ultrasonic waves with respect to fluid such as blood flow, diagnosis information regarding the fluid. Patent Document 1, for example, describes a technique of obtaining, based on a received signal (echo data) obtained by transmitting and receiving ultrasonic waves with respect to fluid within a human body, two-dimensional velocity vectors regarding the fluid at a plurality of points within an observation plane. It is possible to extract, from a distribution of the two-dimensional velocity vectors at a plurality of points within the observation plane, diagnosis information such as a streamline representing a flow of fluid. Application of such information to diagnosis of a heart, for example, is expected.